The present invention relates to a paper feed apparatus used in a copying machine for feeding paper.
A large-capacity feeder (hereinafter referred to as LCF) is an apparatus that can singly store 3,000 to 4,000 paper sheets. The frequency of paper supply can be reduced by storing the LCF with paper sheets of a size that is used frequently.
In this LCF, a paper carrying tray is moved up and down by means of an elevator mechanism, and a paper feed section feeds the uppermost one of paper sheets on the tray.
If a door of the LCF is opened for paper supply, however, the paper carrying tray moves to its lowest position so that paper can be inserted.
If the number of paper sheets to be supplied is small, however, the paper carrying tray moves to the lowest position when the door is opened for paper supply. After the paper supply, therefore, it takes time for each paper sheet to be situated in a paper feed position.
If the paper carrying tray has a storage capacity of 4,000 sheets, for example, paper supply cannot be started unless the tray is raised by a margin corresponding to 3,500 sheets when it is supplied with only 500 sheets, which is very wasteful.
Thus, it takes a lot of time to start copying if a small quantity of paper is supplied to the large-capacity paper feed apparatus in a copying machine.
The object of the present invention is to shorten the release time after paper supply if a small quantity of paper is supplied to a large-capacity paper feed apparatus.
In order to achieve the above object, there is provided a paper feed apparatus which has a door adapted to be opened and closed as paper is supplied, successively feeds paper on the top portion of a paper carrying tray, and raises the tray as the paper is fed, the paper feed apparatus comprising: a door detector which detects the state, open or closed, of the door; a first detector which is located below a paper feed position by a margin corresponding to a given number of paper sheets and detects the presence of paper; a second detector which is located below the first detector and detects the presence of paper; first lowering means which lowers the paper carrying tray to a position where the second detector ceases to detect the presence of paper if the door detector detects the open state of the door; second lowering means which lowers the paper carrying tray to the position where the second detector ceases to detect the presence of paper if the first and second detectors detect the presence of paper; and raising means which raises the paper carrying tray so that the uppermost one of paper sheets on the tray is situated in the paper feed position if the door detector detects the closed state of the door after the tray is lowered by means of the first or second lowering means.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.